This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A064081 #19 Feb 22 2025 09:57:10 %S A064081 4,3,31,13,781,7,19531,313,15751,521,12207031,601,305175781,13021, %T A064081 315121,195313,190734863281,5167,4768371582031,375601,196890121, %U A064081 8138021,2980232238769531,390001,95397958987501,203450521,3814699218751,234750601,46566128730773925781,464881,1164153218269348144531 %N A064081 Zsigmondy numbers for a = 5, b = 1: Zs(n, 5, 1) is the greatest divisor of 5^n - 1^n (A024049) that is relatively prime to 5^m - 1^m for all positive integers m < n. %C A064081 By Zsigmondy's theorem, the n-th Zsigmondy number for bases a and b is not 1 except in the three cases (1) a = 2, b = 1, n = 1, (2) a = 2, b = 1, n = 6, (3) n = 2 and a+b is a power of 2. %H A064081 Robert Israel, <a href="/A064081/b064081.txt">Table of n, a(n) for n = 1..133</a> %H A064081 K. Zsigmondy, <a href="http://dx.doi.org/10.1007/BF01692444">Zur Theorie der Potenzreste</a>, Monatsh. f. Math. 3 (1892) 265-284. %Y A064081 Cf. A024049, A064078, A064079, A064080, A064082, A064083. %K A064081 nonn %O A064081 1,1 %A A064081 _Jens Voß_, Sep 04 2001 %E A064081 More terms from _Vladeta Jovovic_, Sep 06 2001 %E A064081 Definition corrected by _Jerry Metzger_, Nov 04 2009 %E A064081 More terms from _Robert Israel_, Feb 21 2025